Water sensitive carboxyl containing polymers of vinylidene monomers containing at least one terminal CH.sub.2 &lt; group are well known. Such polymers may be homopolymers or copolymers with other vinylidene monomers, of unsaturated polymerizable carboxylic acids such as acrylic acid, methacrylic acid, maleic acid or the anhydride, itaconic acid and the like. The polymers of these acids are usually cross-linked with small amounts of cross-linking agents, present during polymerization, which, in the form of their salts, absorb large quantities of water or other liquids. These polymer materials are normally prepared by polymerization with free radical forming catalysts in organic media such as benzene or halogenated hydrocarbons which are solvents for monomers but are non-solvents for the resulting polymers. During the course of such polymerization, the polymer begins to precipitate from solution as it is formed and forms a slurry in the solvent which may cause processing problems at high total solids contents. Since benzene and many of the halogenated hydrocarbons are not preferred for use in some industrial applications, and since in many applications for the water swellable polymers, certain petroleum based solvents such as mineral spirits is the desired solvent used, slurries of the polymers in mineral spirits and the like are desired. However, polymerizations in mineral spirits have caused some processing problems and changes in some physical properties of the polymers and may require modification of normal polymerization processes. Other techniques for obtaining mineral spirit slurries of water sensitive carboxyl containing polymers are desired, particularly processes that could provide higher total solids slurries than readily obtainable by direct polymerization in large scale equipment.